Understanding of Chain.dofilter (Request,response)

His role is to forward the request to the next object on the filter chain. What's the "down" point here?

refers to the next filter, if there is no filter that is the resource you requested.

General filter is a chain, Web. XML is configured with several. and one by one.

Request resource, Filter2->filter3---Filter1

Here is an example: input.jsp is used to submit input, when submitted, the filter detects the name and age, if the entire regular will be submitted to output.jsp, if not normal to erroroutput.jsp. There is also a filter, It is used to detect whether a page has character encoding set, if not. (prevents garbled problems). ==================Encodefilter.java===================package Servletbean;public class Encodefilter implements Filter {public void DoFilter ( ServletRequest request, servletresponse response, Filterchain chain) throws IOException, servletexception {if ( Request.getcharacterencoding () ==null) {System.out.println (encoding); request.setcharacterencoding (encoding);} Chain.dofilter (request, response);//To the next chain}public void Init (Filterconfig fconfig) throws Servletexception {This.config =fconfig;encoding=fconfig.getinitparameter ("Encoding");} }==============input.jsp==============<form action= "output.jsp" name= "form" method= "POST" ><table><tr><td>name< /td><td><input type= "text" name= "name"/></td></tr><tr><td>age</td> <td><input type= "text" name= "age"/></td></tr><tr><td><input type= "Submit" Name= "OK" value= "OK"/></td></tr></table></form>Myfilter.java======================package Servletbean;import Javax.swing.joptionpane; public class Myfilter implements Filter {public void DoFilter (ServletRequest request, servletresponse response, Filterchain chain) throws IOException, Ser Vletexception {   response.setcontenttype ("text/html");  response.setcharacterencoding ("GB2312");   PrintWriter out=response.getwriter ();  string Name= "";  string age= "";  int age1;  name= Request.getparameter ("name");  Age=request.getparameter ("Age");  RequestDispatcher dispatch= Request.getrequestdispatcher ("erroroutput.jsp");    if (name==null| | name== "" | | name== "" | | Age==null) {Joptionpane.showmessagedialog (null, "User name and age input Error!) ");d Ispatch.forward (request, response); return;} Else{try{age1=integer.parseint (age);} catch (Exception e) {//joptionpane.showmessagedialog (null, "age must be a number! ");d Ispatch.forward (request,response); return;//If the error page is in erroroutput.jsp}}Chain.dofilter (Request, response);//here is said to be correct, that is, he went back to find the next chain, but it has no, so it will go to jump page, at this time to jump to the page is action= "output.jsp". }}================Web. XML=============== Note: Filter is in order <filter><description></description><display-name> Encodefilter</display-name><filter-name>encodefilter</filter-name><filter-class>   Servletbean.encodefilter</filter-class><init-param> <param-name>encoding</param-name> <param-value>GB2312</param-value></init-param></filter><filter-mapping>< Filter-name>encodefilter</filter-name><url-pattern>/*</url-pattern></filter-mapping ><filter><description></description><display-name>myfilter</display-name>< filter-name>myfilter</filter-name><filter-class>servletbean.myfilter</filter-class></ filter><filter-mapping><filter-name>myfilter</filter-name><url-pattern>/output.jsp </url-pattern></filter-mapping>

Understanding of Chain.dofilter (Request,response)